Stargate was originally planned as the first in a film franchise. However, the pair became involved in other projects (Independence Day, Godzilla, etc.), and abandoned Stargate. Emmerich and Devlin do not consider Stargate SG-1 a valid continuation of their film.
Emmerich's films have grossed $2.7 billion worldwide, more than those of any European-born director and making him the country's 14th-highest grossing director of all time.